Black hole thermodynamics

In cosmological thermodynamics, black hole thermodynamics is the study of the behaviors of black holes, according to measurements of quanities such as temperature, radiation, energy, entropy, etc., from a thermodynamics system point of view. A noted researcher in this field is American physicist Robert Wald. [2]

History
The term "black hole" was coined in 1967 by American theoretical physicist John Wheeler. [3] The first ideas on the thermodynamical understanding of black holes, traces to early 1970s discussions between Wheeler, the coiner of the term “black hole”, and his graduate student Mexican-born Jewish physicist Jacob Bekenstein. In 1971, Wheeler pointed out to Bekenstein that black holes seem to flout the second law of thermodynamics. [1] In 1972, to remedy this issue, Bekenstein suggested that black holes should have a well-defined entropy. On this premise, Bekenstein formulated the generalized second law of thermodynamics, which states that:

“The sum of black-hole entropy and ordinary entropy outside a black hole never decreases.”

To find and measure this “black hole entropy”, Bekenstein reasoned that, because of the effect that the massive gravity of black holes pulls light, energy, and matter into its body, according to German-born American Albert Einstein’s mass-energy relation E=mc², a black hole's entropy increase must be proportional or related to its surface area. Two years later, in 1974, this postulate was confirmed when British astrophysicist Stephen Hawking discovered that black holes radiate energy, now called Hawking radiation, and hence they must have a correlative temperature and thus an entropy (black hole entropy). [2]

Limitations
In 1992, American particle physicist Steven Weinberg stated the following about black holes and thermodynamics: [4]

“Thermodynamics applies to black holes, not because they contain a large number of atoms, but because they contain a large number of fundamental mass units of the quantum theory of gravitation, equal to about one hundred thousand of a gram and known as the Planck mass. It would not be possible to apply thermodynamics to a black hole that weighted less than a hundred thousandth of a gram.”

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References
1. Wald, Robert M. (1994). Quantum Field Theory in Curved Spacetime and Blackhole Thermodynamics. Chicago: The University of Chicago Press.
2. Baeyer, Hans Christian von. (2004). Information - the New Language of Science. Cambridge, (pgs. 205-11). Massachusetts: Harvard University Press.
3. Fabbri, Alessandro and Navarro-Salas, Jose. (2005). Modeling Black Hole Evaporation (pg. 17). Imperial College Press.
4. Weinberg, Steven. (1992). Dreams of a Final Theory: the Scientist’s Search for the Ultimate Laws of Nature (pg. 286). Random House.

Further reading
● Jacobson, Ted. (1996). "Introductory Lectures on Black Hole Thermodynamics" (PDF), (70 pgs). Institute for Theoretical Physics University of Utrecht.
● Wald, Robert M. (2001). "The Thermodynamics of Black Holes" (PDF), (40 pgs). July 09, Living Reviews in Relativity, Max Planck Institute for Gravitational Physics.
Further reading
● Machamer, Peter K. (2002). The Blackwell Guide to the Philosophy of Science (section: black hole thermodynamics, pg. 189). Wiley-Blackwell.
● Chakraborty, Subenoy and Bandyopadhyay, Tanwi. (2008). “The Geometry of Black Hole Thermodynamics in Gauss-Bonnet Theory” (Abs), Classical Quantum Gravity. 25, 6-pgs.

External links
Black hole thermodynamics - Wikipedia.
Black hole thermodynamics - Knowing the universe and its secrets.

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